首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   5670篇
  免费   413篇
  国内免费   14篇
耳鼻咽喉   72篇
儿科学   149篇
妇产科学   74篇
基础医学   746篇
口腔科学   34篇
临床医学   696篇
内科学   1098篇
皮肤病学   53篇
神经病学   542篇
特种医学   260篇
外科学   1104篇
综合类   85篇
一般理论   5篇
预防医学   451篇
眼科学   99篇
药学   325篇
中国医学   4篇
肿瘤学   300篇
  2023年   45篇
  2022年   98篇
  2021年   235篇
  2020年   96篇
  2019年   176篇
  2018年   191篇
  2017年   147篇
  2016年   158篇
  2015年   204篇
  2014年   288篇
  2013年   319篇
  2012年   440篇
  2011年   447篇
  2010年   220篇
  2009年   207篇
  2008年   327篇
  2007年   306篇
  2006年   285篇
  2005年   280篇
  2004年   248篇
  2003年   245篇
  2002年   226篇
  2001年   68篇
  2000年   53篇
  1999年   42篇
  1998年   39篇
  1997年   21篇
  1996年   37篇
  1995年   25篇
  1994年   18篇
  1993年   18篇
  1992年   20篇
  1991年   25篇
  1990年   23篇
  1989年   28篇
  1988年   25篇
  1987年   21篇
  1986年   33篇
  1984年   16篇
  1983年   18篇
  1982年   20篇
  1981年   16篇
  1980年   18篇
  1979年   24篇
  1978年   26篇
  1976年   20篇
  1975年   15篇
  1974年   19篇
  1973年   14篇
  1972年   23篇
排序方式: 共有6097条查询结果,搜索用时 15 毫秒
1.
2.
BACKGROUND: Our objective was to determine the cost-effectiveness of a comprehensive, risk-based triage system, composed of multiple critical pathways, with the use of early myocardial perfusion imaging (MPI) in low-risk patients. We found previously that a chest pain evaluation system that uses MPI in low-risk patients was safe and effective, but the cost-effectiveness of this approach was not studied. METHODS AND RESULTS: We compared two groups. The Acute Cardiac Team (ACT) group (n = 874) was assigned prospectively to 1 of 4 risk levels by emergency department (ED) physicians. Level 1, 2, and 3 patients were admitted; level 4 patients were evaluated in the ED. Level 3 and 4 patients underwent ED MPI. The control group (n = 713) represented consecutive patients evaluated in the prior year according to standard care and assigned retrospectively to an ACT level based on the presenting electrocardiographic and clinical data. Record and hospital administrative data were assessed for clinical variables, outcomes, lengths of stay, and all expenses incurred within 30 days of the index visit. The baseline characteristics of the two groups were similar, including age, sex, myocardial infarction prevalence, and 30-day revascularization rates within each level or between the two groups. Mean costs per encounter were reduced for the ACT patients for each level, which was significant when all patients were compared ($5,030 +/- $7,081 vs $6,044 +/- $10,432, P =.02). Use of MPI in the low-risk patients was associated with reduced costs (level 3, $4,958 +/- $4,948 vs $5,051 +/- $7,036; level 4, $1,529 +/- $2,664 vs $1,794 +/- $6,854) and was associated with a significantly lower angiography rate and shorter length of stay. CONCLUSIONS: Implementation of a comprehensive strategy for chest pain evaluation and triage reduced overall costs for patients with chest pain on presentation. Acute MPI in the ED setting did not increase net cost.  相似文献   
3.
4.
Methicillin-resistant Staphylococcus aureus (MRSA) has traditionally been a nosocomial pathogen. However, several recent studies have noted community-acquired MRSA among young, healthy patients with no risk factors or healthcare system exposure. We report the transmission of a strain of community-acquired MRSA in our neonatal intensive care unit.  相似文献   
5.
We investigate the role that the superior colliculus (SC) and the cerebellum might play in generating gaze shifts. The discharge of cells in the intermediate layers of the SC is tightly linked to the occurrence of saccades. Many studies have demonstrated that the cerebellum is involved in both eye and head movements. When the head is unrestrained, large amplitude gaze shifts are composed of coordinated eye and head movements. In this study, we propose that the gaze saccades system is controlled by a feedback loop between the SC and the cerebellum. The SC only encodes retinal coordinates and controls the eye displacement (to move the fovea to the target), while the cerebellum deals with the gaze programming and controls the head displacement. When a target appears in space, the buildup cells within the SC decode the target signal in the retina before the saccade onset, and input the signal of the gaze displacement to the cerebellum. The cells in the cerebellum vermis encode the initial position of the eye in the orbit. The gaze displacement is decomposed into the head amplitude and the eye amplitude within the cerebellum. There are two output signals from the cerebellum. One signal controls the head movement. The other is projected back to the SC, and forms a component of the saccade vector to control the eye movement. The sum of the vectors provided by the cerebellum and the vector provided by the burst cells in the SC indicates the direction and the amplitude of the desired movement of the eye during the saccade. We propose a cerebellum model to predict the displacements of the eye and head under the condition that the position of the target signal in the retina and the initial position of the eye in the orbit are known. The results from the model are close to that observed physiologically. We conclude that before gaze shift onset, the cerebellum may play an important role in decomposing the gaze displacement into an eye amplitude and head amplitude signal.  相似文献   
6.
BACKGROUND: Vitamin D deficiency is a putative, pathogenic cofactor in the increase in osteopenia and osteoporosis seen in patients with Crohn's disease. OBJECTIVE: To determine the frequency of low serum 25-hydroxy-vitamin D3 (25-OHD) levels and the associated alterations in bone mineral density in a cohort of adults with Crohn's disease. METHODS: 25-OHD levels were determined in 242 consecutive patients with Crohn's disease seen in two tertiary inflammatory bowel disease referral centres. Bone mineral density was assessed by dual energy x-ray absorptiometry. RESULTS: Nineteen (8%) patients exhibited vitamin D deficiency (25-OHD less than 25 nmol/L) and 52 (22%) patients exhibited vitamin D insufficiency (25-OHD less than 40 nmol/L). Mean T-scores at the lumbar spine, femoral neck, total hip and ultradistal radius in the group with low 25-OHD did not differ from those of the normal 25-OHD group. Serum alkaline phosphatase and parathyroid hormone levels were higher in the low 25-OHD group than in the normal group. Decreased red blood cell (RBC) folate predicted low 25-OHD in male patients, while smoking, RBC folate and serum iron predicted low 25-OHD in female patients. The rate of low 25-OHD deficiency in the winter was significantly higher than that in the summer (11.9% versus 2.8%, respectively). CONCLUSION: Vitamin D-deficient Crohn's disease patients exhibit biochemical evidence of metabolic bone disease, without detectable differences in bone mineral density. Sunlight exposure, nutrition and smoking status were predictors of vitamin D deficiency in this patient cohort.  相似文献   
7.
8.
J Feil  C Burri  H Kiefer 《Der Orthop?de》1988,17(3):272-278
Both in open and in closed elbow fractures, anatomical joint reconstruction and rigid internal fixation, which permit early initiation of motion, are essential for good joint function. However, in open distal intraarticular humerus fractures this is more difficult to achieve, owing to the high rate of comminuted types C 2 and C 3 fractures. In addition, the extensive soft tissue lesions often mean that physiotherapy cannot be started until later than would otherwise be desirable. This retrospective study shows that the functional results in 60 patients operated on for correction of open distal intraarticular humerus fractures were worse (1/3 "excellent/good", 2/3 "moderate/poor") than those in patients treated for closed fractures. Complications included superficial infection in 7 patients, osteitis in 11, late instability in 10, fatigue failure of the implants in 5, and non-union in 10 patients.  相似文献   
9.
130 medical and 130 administrative heads were asked to fill in a structured questionnaire to obtain an assessment of meals provided in Austrian hospitals. 62 questionnaires in each group were returned fully completed. Meals: ?S 46,--are available per patient and day; whereby the costs of special diets are ?S 11,--higher on average per day. Diets on offer: 96.8% of the questioned hospitals offered a diabetes diet; 95.2% a weight-reducing diet, 93.5% a light balanced diet and diet for patients with hyperlipidaemia and 90.3% a reduced salt diet (the worst accepted by the patients). 90.3% of these hospitals would consider dietary recommendations as a preventive measure. In fact, preventive dietary measure are implemented in 75.5% of the hospitals questioned. It was apparent that the staff in charge are aware of the influence of correct-nutrition in hospitals. It is recommended that nutritional advice should be offered more often in all wards (this is at present available in only 8.0% of the hospitals). It should be mentioned that financial resources concerning hospital meals should be increased for the more widespread establishment of "healthy food", too.  相似文献   
10.
Interneuronal networks in neocortex underlie feedforward and feedback inhibition and control the temporal organization of pyramidal cell activity. We previously found that lower layer neocortical interneurones can reach action potential threshold in response to the stimulation of a single presynaptic cell. To better understand this phenomenon and the circuit roles of lower layer neocortical interneurones, we combined two-photon calcium imaging with whole cell recordings and anatomical reconstructions of low threshold spiking (LTS) interneurones from mouse neocortex. In both visual and somatosensory cortex, LTS interneurones are somatostatin-positive, concentrated in layer 5 and possess dense axonal innervation to layer 1. Due to the LTS properties, these neurones operate in burst and tonic modes. In burst mode, dendritic T-type calcium channels boosted small synaptic inputs and triggered low threshold calcium spikes, while in tonic mode, sodium-based APs evoked smaller calcium influxes. In both modes, the entire dendritic tree of LTS interneurones behaved as a 'global' single spiking unit. This, together with the fact that synaptic inputs to layer 5 LTS cells are facilitating, and that their axons target the dendritic region of the pyramidal neurones where bursts are generated, make these neurones ideally suited to detect and control burst generation of individual lower layer pyramidal neurones.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号